The kudzu bug situation has very quickly become a real problem for Virginia soybean producers. We are getting reports of infestations in the South Boston area and one from near Yale in Sussex County. I am quite sure that there are more infested fields. The image sent to me from the Yale field showed at least a dozen KB adults on a single plant. WHAT IS THE THRESHOLD and WHEN SHOULD YOU TREAT???
The treatment threshold for full grown R-stage plants has not changed (see below), but I have new information on thresholds for seedling/vegetative stage plants. Based on an experiment in GA, they (and others) are recommending treating at V2-V3 stage at an average of 5 bugs (adults and/or nymphs) per plant. The threshold increases to 10 bugs per plant for plants from 1-2 feet tall. The established threshold of one nymph per sweep (one swoosh of the net) should be used for plants above 2 feet tall. Plants should be sampled at least 50 feet from the edge of the field. The reason for this is that the adults have an extended migration period (6-8 weeks) and colonize field edges first. If you sample the edges, chances are you will make a spray decision too soon before the migration is over. They stress that these thresholds are PRELIMINARY and will absolutely change as we get more information.
Here is a ‘cautionary tale’ provided by Dr. Reisig at NCSU—“A NC grower noticed kudzu bugs on the edge of his April-planted beans in May 2012. They had not yet infested the interior portions of the field. He opted to spray. He then had to spray again in June, as the adults remigrated into the field. Additionally, sprays don’t kill eggs, so these hatched into nymphs. The grower then had to spray a 3rd time in June, as spider mites were flared in the field from the lack of beneficial insects. We want to avoid these costly situations while still preserving our yield.”
Off and running.

We are almost certainly going to have some problems with kudzu bug (KB) in soybean fields this summer. Why? We have been getting very early reports of adults from several southeastern counties for at the past several weeks (including Suffolk, Isle of Wight, Sussex, Dinwiddie, Greensville and Prince George). Likely they are much more wide spread. Adults are good fliers and land on clothing, vehicles, houses and other plants. Attached (hit the ‘more’ button) is an image just forwarded by Scott Reiter in Prince George County of adults that were found on a fig tree. Dr. Jeremy Greene (Entomologist, Clemson) shared that….”KBs can be numerous on fig trees. Although they are undoubtedly feeding to some extent, we do not think they are an issue on fig trees. We are recommending that they be sprayed with soapy water or insecticidal soap on these transient hosts in yards as they cause a nuisance. Dish washing detergent will kill or run them off.”
As you may recall, last summer in our Virginia soybean field surveillance program we observed adult KBs in soybean fields in 16 or so counties but not until well into the season. We reckoned that those adults had migrated from the south. A few nymphs were also found in a couple of locations. No fields became infested at treatable levels.
By contrast, this year’s very early adult activity means fields are at much greater risk. According to the folks in South Carolina and Georgia who have been working with kudzu bug since its first occurrence in soybean in 2009, this very early adult activity means a couple of significant things—one, the adults we are seeing now overwintered (in the adult stage) locally. This is a much different picture than what we had last summer and likely means we are at the beginning of having to manage them in fields. And two, they will begin to invade soybean fields as soon as they start flowering.
Most alarming is the report and image I just received (May 22) from Jim Oliver (Monsanto) that shows a volunteer soybean plant from the South Boston area covered with KB nymphs. This is the first record of a heavy nymphal infestation on soybean in Virginia. The nymphs are congregating on some of the 8-10 inch tall volunteer soybeans but not (yet) on the newly planted beans in that field that are about 3 inches tall. My advice was to wait to see if they move to the planted crop before making a control decision.
Fortunately, we do not have to ‘reinvent the wheel’ in terms of management recommendations—just stick with what has been developed in Georgia and South Carolina where they have had a couple of years of experience and research. First, infestations are most likely to be encountered in the earliest planted, full season, earliest maturity group soybean fields as those will be the first to flower. Second, the threshold is based on numbers of nymphs, NOT adult activity. Basically, we need to key on the nymphal stage of this insect in soybeans. Fields should be treated when the average reaches one nymph per sweep net sweep or if nymphs are easily found on stems, leaf petioles or leaves. Because there are only two complete generations per year, we should be able to control the nymphs for each generation and control population development. Third, there are several good insecticide options for controlling KB. We will provide more detail on these in future Advisories. These recommendations as well as good images of the different insect stages (egg, nymph, adult) are located in a kudzu bug field guide produced by Clemson University, University of Georgia and the United Soybean Board available online at: http://digital.turn-page.com/i/87846
Our advice, begin checking any soybean fields where plants have emerged, especially if you are located in the south central part of the state.
Additional information: kudzu-bug-adults-s-reiter-may-20-2013-jpg